Carbon dioxide is now regarded as a promising refrigerant as a substitute for ion gases in the industrial or domestic freezers or refrigerators, or domestic air conditioners, car air conditioners, etc., but involves such problems as permeation of carbon dioxide into seal materials (wing to a high solubility of carbon dioxide into polymer materials such as rubber, etc., or generation of blisters due to pressure changes in the use circumstances.
The present applicant have already proposed a butyl rubber composition, a resin/EPDM-based thermoplastic elastomer, etc. as carbon dioxide seal materials, but further improvements have been desired for the butyl rubber with respect to the heat resistance characteristics and for the thermoplastic elastomers with respect to the low-temperature characteristics.    Patent Document 1: JP-A-2002-53718    Patent Document 2: JP-A-10-231471
Compositions comprising hydrogenated NBR, EPDM or the like are also known as carbon dioxide seal materials. However, hydrogenated NBR has a distinguished carbon dioxide impermeability, but generally suffers from a high hardness and a large compression set, and thus the sealability as gasket materials is not satisfactory, as compared with other materials. EPDM has distinguished heat resistance and sealability, but still now fails to satisfy the carbon dioxide impermeability and foaming resistance.    Patent Document 3 JP-A-2003-246976    Patent Document 4 JP-A-2003-212361